1. Field of the Invention
The present invention relates to pressure-sensitive adhesive sheets for use in the field of medical hygiene materials and more particularly to medial pressure-sensitive adhesive sheets for use in first-aid adhesive bandages, large adhesive bandages, pressure-sensitive bandages, dressing materials and the like.
2. Description of Related Art
Pressure-sensitive adhesives commonly used for the pressure-sensitive adhesive layers of pressure-sensitive adhesive tapes include pressure-sensitive adhesives comprised by (meth)acrylate polymers that have excellent adhesion and excellent moisture permeability as well as low chemical stimulation to the skin. Incidentally, the pressure-sensitive adhesives comprised by (meth)acrylate polymers may often cause users to feel pain or give damage to the corneum or epidermis of the skin when the pressure-sensitive adhesive tape if peeled from the skin because of strong adhesion of the adhesives comprised by the (meth)acrylate polymers. In particular, when pressure-sensitive adhesive tapes are applied to the same site repeatedly, damage of the skin accompanied by bleeding could occur, which raises a big problem.
To reduce such physical stimulations to the skin, there have been proposed pressure-sensitive adhesives obtained by adding, to a (meth)acrylate polymer, a large amount of liquid component compatible with the polymer, and subjecting the resultant to crosslinking treatment to bring it into a gel state as described in JP-A-06-23029 and JP-A-06-319793. For example, such pressure-sensitive adhesives can alleviate and scatter the stress given to the surface of the skin at the time of peeling off while retaining high adhesion attributable to the (meth)acrylate polymer. Therefore, the adhesives have less physical stimulation to the skin and do not cause peeling-off of the corneum and the like, so that they are used in transdermal drug delivery patches and medical surgical tapes.
However, lamination of the pressure-sensitive adhesive disclosed in the above-mentioned publications on films to form pressure-sensitive adhesive tapes results in migration of the liquid components in the pressure-sensitive adhesive into the films to swell the films, thus causing deformation. As a result, the processability of the pressure-sensitive adhesive sheets by, for example, punching is extremely reduced.